qt: Fix joystick dialog size.

Set fixed size as a constraint to allow the dialog conform to selections
instead of staying the initial minimum size.

src/qt/qt_joystickconfiguration.cpp

@@ -43,7 +43,7 @@ JoystickConfiguration::JoystickConfiguration(int type, int joystick_nr, QWidget
     }
 
     ui->comboBoxDevice->setCurrentIndex(joystick_state[joystick_nr].plat_joystick_nr);
-    setFixedSize(minimumSizeHint());
+    layout()->setSizeConstraint(QLayout::SetFixedSize);
 }
 
 JoystickConfiguration::~JoystickConfiguration()
@@ -197,6 +197,4 @@ void JoystickConfiguration::on_comboBoxDevice_currentIndexChanged(int index) {
 
         ++row;
     }
-
-    setFixedSize(minimumSizeHint());
 }